[REGRESSION] in 3.18-rc1: ppp crashes kernel

[Stefan Seyfried]

Hi all,

since 3.18-rc1, setting up a PPP interface kills my kernel with

[  163.433251] PPP generic driver version 2.4.2
[  164.452474] ------------[ cut here ]------------
[  164.453327] kernel BUG at ../mm/vmalloc.c:1316!
[  164.453327] invalid opcode: 0000 [#1] PREEMPT SMP 
[  164.453327] Modules linked in: ppp_async crc_ccitt ppp_generic slhc af_packet xfs libcrc32c coretemp kvm_intel 
snd_hda_codec_conexant iTCO_wdt snd_hda_codec_generic iTCO_vendor_support uvcvideo snd_hda_intel snd_hda_controller mac80211 videobuf2_vmalloc snd_hda_codec kvm e1000e videobuf2_memops cfg80211 videobuf2_core v4l2_common snd_hwdep i2c_i801 videodev snd_pcm pcspkr thinkpad_acpi serio_raw wmi lpc_ich snd_timer thermal snd rfkill mfd_core tpm_tis shpchp mei_me soundcore ptp mei pps_core acpi_cpufreq tpm battery processor ac dm_mod btrfs xor raid6_pq i915 i2c_algo_bit drm_kms_helper drm video button sg
[  164.453327] CPU: 0 PID: 6927 Comm: pppd Not tainted 3.18.0-rc3-3.ge706e91-desktop #1
[  164.453327] Hardware name: LENOVO 7470E36/7470E36, BIOS 6DET61WW (3.11 ) 11/10/2009

This is easy to reproduce with:

linux:~ # cat bin/crashme.sh 
----
#!/bin/bash -x
pppd local pty "netcat -l 1234" &
sleep 1
pppd local pty "netcat localhost 1234" &
sleep 1
----

3.17 works fine.
I bisected the issue multiple times and always arrived at

# first bad commit: [d6dd50e07c5bec00db2005969b1a01f8ca3d25ef] Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

which is a merge commit unfortunately.

The BUG encountered above is in:

1309 static struct vm_struct *__get_vm_area_node(unsigned long size,
1310                 unsigned long align, unsigned long flags, unsigned long start,
1311                 unsigned long end, int node, gfp_t gfp_mask, const void *caller)
1312 {
1313         struct vmap_area *va;
1314         struct vm_struct *area;
1315 
1316         BUG_ON(in_interrupt());
1317         if (flags & VM_IOREMAP)
1318                 align = 1ul << clamp(fls(size), PAGE_SHIFT, IOREMAP_MAX_ORDER);
1319 

the call trace is:
[  164.453327] Call Trace:
[  164.453327]  [<ffffffff811974bd>] __vmalloc_node_range+0x6d/0x290
[  164.453327]  [<ffffffff8119771e>] __vmalloc+0x3e/0x50
[  164.453327]  [<ffffffff81146950>] bpf_prog_alloc+0x30/0xa0
[  164.453327]  [<ffffffff8157b716>] bpf_prog_create+0x46/0xb0
[  164.453327]  [<ffffffffa07ecb90>] ppp_ioctl+0x420/0xe9a [ppp_generic]
[  164.453327]  [<ffffffff811df1c7>] do_vfs_ioctl+0x2e7/0x4c0
[  164.453327]  [<ffffffff811df421>] SyS_ioctl+0x81/0xa0
[  164.453327]  [<ffffffff8165ee2d>] system_call_fastpath+0x16/0x1b
[  164.453327]  [<00007f4502d87397>] 0x7f4502d87397

I have a crashdump of the kernel, but given this is easily reproducible, I doubt
that I need to send this to anyone :-)

Best regards,

	Stefan

-- 
Stefan Seyfried
Linux Consultant & Developer -- GPG Key: 0x731B665B

B1 Systems GmbH
OsterfeldstraÃe 7 / 85088 Vohburg / http://www.b1-systems.de
GF: Ralph Dehner / Unternehmenssitz: Vohburg / AG: Ingolstadt,HRB 3537
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